Biodegradable quantum dot nanocomposites enable live cell labeling and imaging of cytoplasmic targets

Semiconductor quantum dots (QDs) offer great promise as the new generation of fluorescent probes to image and study biological processes. Despite their superior optical properties, QDs for live cell monitoring and tracking of cytoplasmic processes remain limited due to inefficient delivery methods available, altered state or function of cells during the delivery process and the requirement of surface-functionalized QDs for specific labeling of subcellular structures. Here, we present a noninvasive method to image subcellular structures in live cells using bioconjugated QD nanocomposites. By incorporating antibody-coated QDs within biodegradable polymeric nanospheres, we have designed a bioresponsive delivery system that undergoes endolysosomal to cytosolic translocation via pH-dependent reversal of nanocomposite surface charge polarity. Upon entering the cytosol, the polymer nanospheres undergo hydrolysis thus releasing the QD bioconjugates. This approach facilitates multiplexed labeling of subcellular structures inside live cells without the requirement of cell fixation or membrane permeabilization. As compared to conventional intracellular delivery techniques, this approach allows the high throughput cytoplasmic delivery of QDs with minimal toxicity to the cell. More importantly, this development demonstrates an important rational strategy for the design of a multifunctional nanosystem for biological applications.     

Nanoparticle-mediated cellular response is size-dependent

Nanostructures of different sizes, shapes and material properties have many applications in biomedical imaging, clinical diagnostics and therapeutics. In spite of what has been achieved so far, a complete understanding of how cells interact with nanostructures of well-defined sizes, at the molecular level, remains poorly understood. Here we show that gold and silver nanoparticles coated with antibodies can regulate the process of membrane receptor internalization. The binding and activation of membrane receptors and subsequent protein expression strongly depend on nanoparticle size. Although all nanoparticles within the 2-100 nm size range were found to alter signalling processes essential for basic cell functions (including cell death), 40- and 50-nm nanoparticles demonstrated the greatest effect. These results show that nanoparticles should no longer be viewed as simple carriers for biomedical applications, but can also play an active role in mediating biological effects. The findings presented here may assist in the design of nanoscale delivery and therapeutic systems and provide insights into nanotoxicity.     

Ordinal judgments of symbolic stimuli by capuchin monkeys (Cebus apella) and rhesus monkeys (Macaca mulatta): The effects of differential and nondifferential reward.

Ordinal learning was investigated in capuchin monkeys (Cebus apella) and rhesus monkeys (Macaca mulatta). In Experiment 1, both species were presented with pairings of the Arabic numerals 0 to 9. Some monkeys were given food rewards equal to the value of the numeral selected and some were rewarded with a single pellet only for choosing the higher numeral within the pair. Both species learned to select the larger numeral, but only rhesus monkeys that were differentially rewarded performed above chance levels when presented with novel probe pairings. In Experiment 2, the monkeys were first presented with arrays of 5 familiar numerals (from the range 0 to 9) and then arrays of 5 novel letters (from the range A to J) with the same reward outcomes in place as in Experiment 1. Both species performed better with the numerals, suggesting that an ordinal sequence of all stimuli had been learned during Experiment 1, rather than a matrix of two-choice discriminations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

New didactics for university instruction: why and how?

Why should instructors in traditional higher education institutions consider the re-design of their courses? The paper begins with a defense of four compelling reasons for changes in didactics: a review of some key principles of good teaching and learning, the increasing diversity of student characteristics and associated needs, the strategic and educational rationales for five types of flexibility increase in our current courses, and the particular need for instructors in faculties of education to provide leadership and models. Given the why, the next question is how? The remainder of the paper discusses the how in terms of a conceptually grounded approach to the pedagogical re-engineering of existing courses so that they become more flexible, with more student engagement, more-targetted communication, and more-attuned instructor scaffolding of increased student responsibility for his or her own learning. These concepts are made concrete through the extension of six standard sets of course-related tasks into redesigned sets involving the new didactics and WWW-based course-support functionalities. Examples from current practice at the Faculty of Educational Science and Technology at the University of Twente are used to illustrate the new didactical categories and their use of WWW-based course environments. The paper concludes with a consideration of key challenges that will confront the implementation of such new didactics in practice.     

Some thermodynamic and kinetic properties of the system PETG-CO2, and morphological characteristics of the CO2-blown PETG foams

The solubility of CO₂ in PETG, a glycol-modified PET, was measured at different temperatures and over a broad pressure range, and diffusion coefficients were derived at the corresponding conditions. The solubility of CO₂ is quits high. For example, almost 15 wt% CO₂ can be dissolved in PETG at 35°C and 6.0 MPa. Consequently, CO₂ is good blowing agent for PETG. Cellular foams in the density range of about 0.04 to 1.2 g/cm³ and diameters in the range of about 10 to 150 µm were produced. The foam density and the cell size were found to depend on the foaming temperature and time, with larger cells obtained at higher temperatures or when the sample was foamed for a longer time. The foam density decreased with an increase in the foaming temperature to about 90°C, beyond which the density tended to increase slightly due to the cell collapse or coalescence. The density reduction also depended on the pressure at which the polymer was saturated with CO₂; the higher the saturating pressure at a given temperature, the greater the density reduction.     

Embedding Pyramids into 3D Meshes

The pyramid architecture is a powerful topology in the area of computer vision. On the other hand, the 3D mesh architecture possesses rich topological features which make it suitable for building scalable parallel processor systems. The usefulness of these two architectures has led us to consider the problem of embedding pyramids into 3D meshes, for which we present two solutions. The first solution, termednatural embedding,maps a pyramid into a 3D mesh such that each level of the pyramid is mapped to a single level of the 3D mesh. The second solution, termedmultiple embedding,allows simultaneous embedding of multiple pyramids into a single 3D mesh. The quality of both solutions is evaluated using dilation and expansion measures. Using the multiple embedding, we are able to obtain an average dilation of 1.26 and a near-optimal expansion of 1.12.     

Functionalized polymer foams as metal ion chelating agents with rapid complexation kinetics

Foams prepared from vinylbenzyl chloride and crosslinked with divinylbenzene were functionalized with trialkylphosphite and tetralkylvinylidene diphosphonate. It was determined that the foams could be uniformly functionalized. Batch studies with the functionalized foams show that high levels of metal ion complexation can be achieved. Foams may therefore offer an important alternative to beads for rapid complexation reactions due to their highly porous structure. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1911–1916, 1998     

Structure–property correlation for thin films of semi-interpenetrating polyimide networks. I. Miscibility,curing, and morphology studies

Three different semi-interpenetrating polymer network (semi-IPN) polyimide systems were prepared through blending in solution by using 2 different polyimides, BPDA–PDA and PMDA–ODA (E), and 2 different oligomers, bismaleimide (MDAB) and phenylthynyl-terminated BPDA–PDA (BPDA–PDA–PEPA) oligomers. The oligomers are used as crosslinkers to modify the morphology of polyimides. The results show that both MDAB and PEPA are miscible with BPDA–PDA, but MDAB is immiscible with PMDA–ODA (E). Fourier transform infrared spectrum, dynamic mechanical thermal analysis data, and calculated crosslinking density indicate that there are crosslinking networks in these semi-IPN polyimide systems. In addition, the density and wide-angle X-ray diffraction results confirm that the molecular ordering and packing order are reduced by the addition of oligomers for these semi-IPN polyimide systems. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 261–272, 1998     

Depletion of tylosin residues in feathers,muscle and liver from broiler chickens after completion of antimicrobial therapy

Tylosin is one of the most commonly used antimicrobial drugs from the macrolide family and in broiler chickens it is used specially for the treatment of infectious pathologies. The poultry industry produces several by-products, among which feathers account for up to 7% of a chicken’s live weight, thus they amount to a substantial mass across the whole industry. Feathers have been repurposed as an animal feed ingredient by making them feather meal. Therefore, the presence of high concentrations of residues from antimicrobial drugs in feathers might pose a risk to global public health, due to re-entry of these residues into the food chain. This work aimed to characterise the depletion behaviour of tylosin in feather samples, while considering its depletion in muscle and liver tissue samples as a reference point. To achieve this goal, we have implemented and validated an analytical methodology suitable for detecting and quantifying tylosin in these matrices. Sixty broiler chickens, raised under controlled conditions, received an oral dose of 32 mg kg^-1 of tylosin for 5 days. Tylosin was quantified in muscle, liver and feathers by liquid chromatography coupled with a photodiode array detector (HPLC-DAD). High concentrations of tylosin were detected in feather samples over the whole experimental period after completing both the therapy and the recommended withdrawal time (WDT). On the other hand, tylosin concentrations in muscle and liver tissue samples fell below the limit of detection of this method on the first sampling day. Our results indicate that the WDT for feather samples is 27 days, hence using feather meal for the formulation of animal diets or for other agricultural purposes could contaminate with antimicrobial residues either other livestock species or the environment. In consequence, we recommend monitoring this matrix when birds have been treated with tylosin, within the context of poultry farming.